Body Condition and Reproductive Performance of Broodmares

The body condition scoring system is a scientific method used to evaluate the condition of the horse based on the amount of fat on the horse's body. This article explains the different areas to evaluate when scoring a horse's body condition, as well as details to consider when scoring a horse

David W. Freeman, OSU Extension Equine Specialist

Body condition refers to the amount of fat on a horse’s body. Fat is tissue that serves to store energy and is produced when the horse is digesting more energy than is needed for maintenance and production processes. Over time, horses consuming rations with more energy than is needed will increase body fat. Horses receiving less energy per day than is needed will use significantly increased amounts of fat for an energy source, which decreases the amount of body fat.

Much of this body fat is subcutaneous, meaning fat accumulates in layers immediately below the horse’s skin. This fat cover can be visibly assessed in several specific locations on the horse’s body (Figure 1). The desired level of body condition will vary between horses. As a rule, horses used in athletic performance will maintain a lower body condition than non-performing horses. Additionally, horses will vary in the optimal body condition for productive functions because of individual differences. For example, one horse may perform athletic competition more effectively in a thinner condition as compared with another individual performing the same task in a heavier body condition.

The ability to accurately assess body condition allows horse owners to make ration adjustments that maintain horses at desired fat levels. A universally used scoring system assists communication between horse owners. Moreover, it aids in the application of recommendations to maintain desired levels of body condition for production and management.

Using Body Condition Scores to Quantify Body Condition

The most tested and universal scoring system for assessing body condition was developed by researchers at Texas A&M University in the early 1980s. Since that time, nutritionists, breeding and farm managers, trainers of performance horses, veterinarians, those involved with evaluating animal welfare, and other equine professionals have incorporated the scoring system into their businesses.

This scoring system places the body condition of horses on a scale of one to nine, and provides descriptions which are used to assess fat accumulation along the neck, withers, over the ribs, behind the shoulder, around the tailhead, and the crease on the back. While the scoring system can be used on all horses, it was initially developed to quantify the influence of body condition on the reproductive performance of mares.

Body Condition and Reproductive Performance in Broodmares

Extensive research and field trials document that reproductive efficiency of mares is affected by body condition.

Non-bred mares managed in a body condition of four or less will delay the time of their first ovulation of the breeding season. This delay can be three to four weeks, as compared with mares in a body condition of five or greater. It is significant when breeding managers intend to settle open mares in the early part of the breeding season.

Once cycling, mares in a condition of four or less can be expected to require more cycles per conception. Research on one group of mares resulted in thin mares requiring an average of three cycles before settling, as compared with one and one-half cycles per conception for similarly managed mares with condition scores of five or higher. More cycles per conception results in increased costs for the breeding manager and mare owner.

Pregnancy rates are also affected. Mares in body conditions of four or less have overall pregnancy rate reductions as large as 20 percent less than mares in a greater body condition. Moreover, early pregnancy losses are significantly greater in mares with body scores of four or less.

To summarize, mares in body conditions of four or less will be poor breeders and more susceptible to pregnancy losses than mares maintained at higher body condition scores. Frequently, the onset of cold weather, changes in housing, transportation, foaling and lactation reduce body condition. Thus, recommendations are for mares to enter the foaling and breeding season in body condition scores of six or seven.

One concern expressed by owners is that mares with a body condition greater than five or six will have more trouble foaling. These concerns are unwarranted, as significant research has shown body conditions of seven or greater have no affect on gestation length, length of the foaling process, size of foal or placenta, or measures of foal viability.

Points to Consider

There are several points to consider when using body condition scores.

Although visual appraisal is the primary tool of the scoring system, accuracy will increase when the areas of fat accumulation can be palpated. Long hair can mask the appearance fat. Also, different body conformations greatly affect the visual ability to determine body condition. Taller, larger-framed horses with prominent withers may appear to be leaner than shorter, smaller-framed horses with similar body conditions.

Mares in late gestation may have less fat cover over the ribs because of the influence of the weight of the fetus and associated tissues. Thus, more emphasis should be placed on other locations of fat accumulation.

Horses on large percentage forage diets will typically have larger bellies with lower, distended abdomens than horses being managed on grain or in exercise programs. These “hay bellies” can give the appearance of fat, causing overestimation of body condition.

It is important to recognize specific areas on the horse’s body to assess body condition and to gain experience in identifying body condition on different horses. Periodic reevaluations of individual horses will help to decrease the influence of conformational differences in body condition assessment.

Body condition cannot be altered significantly in short periods of time. Gains in body weight must be made with gradual increases in the ration. The horse’s body requires time to assimilate increases of energy into fat. Also, the incidence of colic and founder will increase when dramatic adjustments in the amount of the daily ration are made. Increasing a mature horse’s body condition from a score of three to a score of six may take four months when the horse is consuming about 1.75 percent of body weight in grain per day, along with unlimited hay. This change in body condition represents an average of 2 1/4 pounds of gain per day, which should be considered near maximal for 1,200-pound broodmares. Environmental stress will increase the length of time and energy intake necessary for increases in body condition.

The above example points out the need to plan well in advance when increasing body condition in horses. Under practical management, increasing body condition at times when production needs for energy are high is difficult and costly. Therefore, allow several months for significant increases in body condition. Similarly, allow for gradual decreases in body condition when physically preparing horses for athletic competition, instead of promoting extreme, sudden weight loss by dramatic restriction of energy.